staging: r8712u: Set device type to wlan

commit 3a21f00a5002b14e4aab52aef59d33ed28468a13 upstream.

The latest version of NetworkManager does not recognize the device as wireless
without this change.

Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>